Article Date: 7/1/2013

New Perspectives on Myopic Foveoschisis

New Perspectives On Myopic Foveoschisis

Surgical techniques can be useful in this complication.

MARY CHAMPION, MD · JOHNNY TANG, MD

Myopic foveoschisis (MFS) is a more recently recognized clinical entity, affecting between 9% and 34% of highly myopic eyes (Figure 1).1-3 In 1958, Phillips described localized posterior retinal detachments in patients with high myopia and posterior staphyloma without the presence of retinal holes,4 postulating that myopic chorioretinal atrophy and the presence of a staphyloma were likely part of the pathogenesis.

Before OCT, it was difficult to distinguish between shallow retinal detachments, macular holes, and foveoschisis in highly myopic patients, particularly because slit-lamp biomicroscopy does not provide a detailed view of the posterior pole of eyes with myopic chorioretinal atrophy.5,6

Takano and Kishi first reported detection of MFS using OCT in 1999, showing foveal retinal detachment and foveoschisis in patients with high myopia with posterior staphyloma.3 Since then, spectral-domain OCT has been shown to be even more sensitive in detecting the pathologies associated with MFS.5

PATHOGENESIS

Studies have suggested the pathogenesis of MFS is multifactorial, involving anterior traction (attachment of contracted vitreous cortex to the retinal surface, epiretinal membrane, retinal vascular traction), rigidity of the ILM, and progression of posterior staphyloma.7-14

The histopathology of myopic foveoschisis has been well documented (Figure 2, page 34).15 The association of premacular structures, such as ERM, and the results of several studies showing anatomical resolution of foveoschisis after vitrectomy with ILM peeling support anterior traction as a key component of MFS.8,16-21

Macular scleral buckling surgeries have also reportedly been successful in MFS, supporting the role of the posterior staphyloma and rigidity of the ILM in MFS.22-24

Histological evaluation of one patient with MFS found that schisis cavities can form in various layers of the neurosensory retina in the macula, including the outer plexiform, inner plexiform, and nerve fiber layers.15

NATURAL HISTORY

Gaucher et al published a long-term evaluation of 29 eyes with MFS and found visual outcomes to be diverse, with some patients (nine of 29) remaining stable for many years and others (20 of 29) with progressively worsening vision or the development of macular holes.8 In the eyes that worsened, the authors noted an association with premacular structures (eg, ERM), supporting the role of anterior traction in development of MFS.

Shimanda et al published a smaller study of eight eyes with MFS followed for at least two years without any surgical intervention. Half of the eyes remained stable in terms of OCT findings and BCVA. The other half experienced decreased BCVA due to macular holes or retinal detachment.14 The authors concluded from this small study that MFS is progressive with possibly poor outcomes, which may justify early surgical intervention.

TREATMENT

The indications for surgery are not clear, given the varied course of the disease demonstrated in these small series and the potential complications of surgical intervention reported.

The presence of premacular structures, reportedly correlated with worse prognosis, could potentially be useful in justifying intervention.8 Some authors advocate surgery for MFS when VA is impaired or the patient complains of visual disturbance.8,18

images

Figure 1. Clinical photographs of the fundus of the right (A) and (B) left eyes in a patient with MFS. (c) Fluorescein angiogram of the right eye in the early (C) and late (D) phases, demonstrating staining of the optic nerve crescents and small window defects along the macular region.

ALL IMAGES FROM TANG J, RIVERS MB, MOSHFEGHI AA, FLYNN HW, CHAN C-C. PATHOLOGY OF MACULAR FOVEOSCHISIS ASSOCIATED WITH DEGENERATIVE MYOPIA. J OPHTHALMOL. 2010;175613, COURTESY OF HINDAWI PUBLISHING CORP.

One recent study suggested early surgery for MFS, particularly in patients with threatened disruption of the outer retina on SD-OCT and in eyes with longer axial length. The authors based this recommendation on SD-OCT findings of persistent photoreceptor defects and irregular choroidal detachments in MFS patients with poor postoperative visual outcomes.21

Vitrectomy With ILM Peeling

Positive postoperative results in several studies, in terms of anatomic resolution of MFS and improved visual acuity, support that pars plana vitrectomy with ILM peeling as a reasonable treatment option for MFS. The basis for PPV with ILM peeling is the assertion that anterior traction on the fovea is at least partially responsible for foveal detachment and retinoschisis.13,17-20,25

The aim of ILM peeling is to relieve anterior traction on the macula and to ensure complete removal of any ERM to avoid recurrence. Removing the rigid ILM may also allow the retina to conform to the posterior staphyloma, which has been shown to contribute to macular detachment in posterior staphyloma.26

images

Figure 2. Photomicrograph (A), with higher magnification (B), of the right eye of a patient demonstrating macular foveoschisis in multiple layers of the retina, including the outer plexiform layer, inner plexiform layer, nerve fiber layer, and the outer plexiform layer in the perifoveal region. Another photomicrograph (C), with higher magnification (D) of the left eye demonstrating classical retinoschisis in the outer plexiform layer, ganglion cell layer, and nerve fiber layer.

The ILM can also act as scaffolding for cellular proliferation after vitrectomy, potentially leading to traction and recurrence of maculopathy.7,27

Zheng et al found that in eyes that underwent PPV with ILM peeling, residual persistent retinoschisis, as well as perimacular tractional tissue and retinal microfolds, could be found in the perifoveal areas at the borders of the peeled ILM. Based on these findings, they speculate that ILM peeling may not only improve MFS, but it may also prevent recurrence due to these residual structures.25

Sayanagi et al also showed that reoperation with ILM peeling on MFS patients, who had previously undergone PPV without ILM (without improvement), provided resolution of MFS and improved VA, supporting the importance of ILM peeling in at least a subset of patients with MFS.13

In another study, electron microscopic examination of the ILM in a patient with recurrence of maculopathy after PPV without ILM showed cellular proliferation on the ILM, suggesting that these cells may have caused tangential traction and induced a retinal detachment and retinoschisis.27

A Controversial Technique

The use of ILM peeling for MFS is not without controversy. ILM peeling is technically difficult in patients with MFS because the ILM is thinner in highly myopic eyes and may be more prone to tearing and iatrogenic macular hole formation.28

Several authors have reported postoperative macular holes,16,18,20,21,28 including one microhole observed intraoperatively.20 Interestingly, anatomic and visual acuity outcomes have been reportedly similar using PPV with and without ILM peeling for MFS.29-31

A compromise that addresses the need for ILM with the concerns for iatrogenic macular hole may be alternative fovea-sparing ILM peeling techniques.32,33 In one study, Shimada et al found that five of the 30 eyes treated with traditional ILM peeling suffered macular holes in the postoperative period, compared to none of the 15 eyes treated with a fovea-sparing ILM peeling technique.

Another study by Ho et al found that a foveola nonpeeling technique resulted in resolution of MFS and improvement in visual acuity in eight of eight patients, with no macular holes. Short follow-ups limited both studies; nevertheless, fovea-sparing ILM peeling techniques could offer an effective alternative that decreases the risk of macular hole.

Whether to Use a Tamponade

Early studies of PPV with ILM peeling for MFS included the use of gas tamponade for foveal reattachment. Some studies have also questioned the necessity of gas tamponade. Several authors have found that PPV with ILM peeling and without gas tamponade resulted in resolution of MFS and foveal reattachment, with an improvement in BCVA, which was comparable to results published by others using gas tamponade.34,35

Panozzo et al concluded that the surgical release of traction was sufficient because this is the main mechanism driving MFS. Additionally, the option of not using a gas tamponade may be more favorable to the patient, because it would not require positioning.

Other studies have found that the gas tamponade led to quicker resolution and may decrease the risk of recurrence, compared to not using a gas tamponade.25,36

The Role of Scleral Buckling

Macular scleral buckling is another alternative for the treatment of MFS. Buckling can avoid the development of cataracts in phakic eyes following PPV (and the need for cataract surgery), as well as the complications associated with ILM peeling.

While PPV with ILM peeling alleviates the internal surface anterior traction, it does not treat the structural contribution of the posterior staphyloma. Scleral buckling addresses this disparity between the retina and the elongated sclera of a staphyloma, which may create shearing forces, stretching, and eventual failure of internal structures, causing MFS.23

Buckling also provides direct mechanical action to bring the RPE closer to the retina, which may provide quicker resolution of foveoschisis than vitrectomy.23

Results With Scleral Buckles

Zhu et al found that posterior scleral reinforcement with a scleral buckle and without PPV improved BCVA and provided anatomical improvement in MFS, similar to PPV. In their small study of 24 eyes treated with scleral buckling, 20 had resolution of foveoschisis, and 18 had improvement in VA. One eye developed a macular hole at the end of the follow-up period, and three patients had recurrence.24

Another small study of six eyes with MFS and retinal detachment without macular hole reported on the use of scleral buckling with a macular plombe.22 All six eyes had morphological resolution of retinoschisis and retinal detachment, and four of the six eyes had improvement in BCVA.

One patient developed subretinal hemorrhage without choroidal neovascularization, with no significant change in vision, and one eye (with pre-existing small subretinal proliferation and hyperfluorescence, which the authors believed was myopic neovascularization) developed subretinal hemorrhage with choroidal neovascularization and decreased vision.22

Mateo et al reported on 16 eyes with MFS treated with scleral buckling and PPV and removal of the posterior hyaloid and without ILM peeling. They initially used a silicone band and then switched to the Ando plombe, designed to be easier and safer than the traditional silicone band.

They found that treatment with both buckling techniques, in conjunction with PPV, provided good results measured as anatomical resolution of MFS and improvement in BCVA.

However, they also found the thin sclera and posterior staphyloma associated with high myopia increased the risk of complications, such as choroidal detachment, which occurred in three patients and spontaneously resolved with no negative effect on vision.

Atrophy of the RPE over the site of the indentation occurred with both buckling procedures, which the authors attributed to local ischemia due to the indentation.23 Other complications included spontaneous extrusion and progressive esotropia requiring explantation. No patients experienced recurrence.

A recent article by Rayes et al presented the results of a novel suprachoroidal buckling technique in 11 patients with MFS.37 The technique involves using a specially designed catheter, inserted into the suprachoroidal space, to inject hyaluronic acid into the area of the staphyloma to indent the choroid.

All patients had resolution of MFS, and vision improved in nine. Complications included choroidal hemorrhage and hyperpigmentation around the area of indentation.

Prognostic Indicators

Prognostic indicators for surgical outcomes in MFS include preoperative VA, which is the most predictive factor for final BCVA after PPV with ILM peeling.18,21,38 A shorter duration of symptoms and shorter axial lengths have also shown correlations with better visual acuity outcomes, and the presence of a foveal detachment showed an association with the greatest improvement in visual outcomes.18,28,38

Greater staphyloma height and preoperative choroidal thinning, as seen on SD-OCT, have demonstrated correlations with poor postoperative VA and with anatomic resolution of MFS following vitrectomy.39

CONCLUSIONS

Myopic foveoschisis affects highly myopic patients with posterior staphyloma. Although the clinical course is not well understood, small studies have shown that foveal detachments and macular holes may occur, resulting in decreased vision.

Successful treatment of MFS has been shown using several surgical options, including PPV with or without ILM peeling (traditional or fovea-sparing), with or without gas tamponade, or even with scleral and suprachoroidal buckling techniques.

Potentially serious complications can arise with these surgical options. Larger prospective, randomized clinical studies are necessary to study the disease course and to evaluate surgical indications. RP

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Mary Champion, MD, is an ophthalmology resident at the University of Kansas Medical Center in Kansas City, KS. Johnny Tang, MD, is associate professor of Ophthalmology at the University of Kansas Medical Center and is director of the medical retina and vitreoretinal surgery service. Neither author reports any financial interests in any of the products mentioned in this article. Dr. Tang can be reached via e-mail at bostonretina@aol.com.



Retinal Physician, Volume: 10 , Issue: July 2013, page(s): 30 - 39